In the production of a high oil content farinaceous composition by extrusion cooking, mobility and immiscibility of the water and oil phases generally increase with increasing temperature. Additionally, the mechanical action of extruder screws tends to increase separation of oil from the remaining mass. The tendency for the oil to separate is at locations within the extruder at which the components are subjected to the highest pressure. Exemplary of high pressure locations in a twin screw extruder are: 1) the space between the extruder screw tips and the die orifice, and 2) the narrowest or more restricted passageways between the left and right hand screw elements.
Oil separation under system pressure (screw or die pressure) can be manifested in extruder surging or uneven mass flow rates from the die. Upon extrusion from the die, separated oil may: 1) appear as a coating on the remaining dough mass, or 2) periodically discharge separately from the remaining dough mass. Nonhomogeneous dough production and discontinuous extruder operation may thus result from oil separation. The problem of oil separation increases with increasing oil levels.
Water separation from flour, up to the boiling point of water, is generally not a problem because of the more hydrophilic properties of flour components such as gluten and starch. As flour and water temperatures are raised, increased migration of water into starch granules, protein (e.g. gluten) denaturization, and starch gelatinization tend to occur. The binding or reaction of water with flour components may promote separation of oil: a) by making the flour components more polar or hydrophilic and b) by creating a greater mass of hydrophilic components.
Conventional cookie production involves forming cookie dough preforms or pieces followed by baking of the pieces. Low temperatures, typically at about room temperature, are used to form the dough. The low temperature mixing generally avoids separation of shortening or fat from hydrophilic dough components. While baking temperatures in a conventional oven, such as a band oven, may promote oil separation, there is no mixing or pressing action performed at the baking temperatures. Any oil separation which may occur in such ovens does not generally interfere with continuous operability of the cookie production process as it would in a continuous cooker/extruder process.
In addition to high temperature mixing and high system pressure, the presence of sugar in a cookie dough may also increase oil and water separation. Solubilization of sugars in water increases the relative amount of the hydrophilic mass. This in turn may tend to promote oil separation.
In the process of the present invention, leavened products are produced using high temperature mixing to promote browning and flavor development and to reduce processing times without the problems caused by the separation of oil from the remaining dough mass. The extruded products of the present invention have a cookie crumb or crumb-like structure and texture and exhibit structural integrity.